1. Field of Application
The present invention relates to the field of electrometallurgy, and more specifically to the equipment for producing ingots by the electroslag remelting process.
2. Description of the Prior Art
Producing ingots, particularly large-size ones, often requires the use of several consumable electrodes. If the ingot shape prevents installation of several electrodes at a time above the slag bath surface, which is the case, e.g. when the shape calls for a narrow mouth in the mould, consumable electrodes are remelted in the mould cavity in succession, one after another. This gives rise to a problem of replacing consumable electrodes in the course of the electroslag process without interrupting its continuity.
Well known in the art as components of electroslag remelting apparatus for producing ingots are means for alternately feeding consumable electrodes into the mould cavity, comprising two swinging electrode holders, one of which during the electroslag process is disposed outside the space above the mould to enable a consumable electrode to be inserted therein, and when a consumable electrode held in another electrode holder is remelted and the resulting stub is withdrawn from the mould cavity by this holder, said first electrode holder takes the place of the latter, while the stub brought outside the mould is replaced by a new consumable electrode (see, e.g. U.K. Pat. Nos. 1,200,278, cl. B3F and 1,355,264, cl. H5H, and U.S. Pat. Nos. 3,587,715 and 3,693,699, cl. 164/252).
Replacing a consumable electrode in the mould cavity by the use of the foregoing means necessarily interrupts the electroslag process at the moment when the stub of a consumed electrode is already withdrawn from, while a new electrode is not yet introduced into the slag bath. Moreover, a new electrode inevitably cools the slag bath. All this results in upsetting the homogeneity of the ingot structure.
Such interruptions of the electroslag process can be avoided by continuously feeding a long electrode or an electrode being built up as it is consumed. Feeding an electrode of an essentially unlimited length is feasible, however, only when its cross-section is relatively small, in which case a wire wound in coils is used as the electrode, while large cross-section electrodes are from piece blanks built up in the course of remelting.
Also known in the art is an electroslag remelting apparatus for producing ingots, including a mould and an electrode feeding device mounted on a supporting stand (see U.S. Pat. No. 3,752,896, cl. 13-18, 1973). The electrode feeding device comprises a lower holder and an upper holder, disposed in succession above the mould and providing for alignment of the consumable electrode and an electrode blank, and a means for joining these, arranged between said holders.
The two holders incorporate fast-acting clamps and are mounted for a vertical movement independently of each other.
While the consumable electrode placed in the clamp of the lower holder and moved by the latter downwardly at a speed corresponding to the remelting rate is being remelted, an electrode blank is placed into the clamp of the upper holder; by the moment when the lower holder reaches its extreme lower position, the upper holder is moved downwardly till the bottom end of the electrode blank comes into abutting contact with the top end of the consumable electrode stub, whereupon these are welded together by said electrode joining means. Next, the clamp of the lower holder is loosened and the latter is moved towards the upper holder, following which the built up electrode is again clamped by the lower holder and released from the clamp of the upper holder.
In the above-described apparatus the remainder of a remelted electrode is built up rather than removed, which excludes slag bath cooling due to introduction of a new electrode. Employing different power sources for weld joining of the consumable electrode and electrode blank and for the electroslag remelting eliminates also the interruptions in the electroslag process.
Said apparatus, however, is inconvenient to operate, calls for much labour for performing the auxiliary operation, and fails to ensure safety of the attending personnel since the process of building up the consumable electrode is relatively complex and involves reciprocating movements of the holders and frequent re-clamping of the blank and electrode, which have to be carried out above an operating mould.
The constructional features of the electrode feeding device in the above-described apparatus make it impossible to automate said operation, especially when more than two electodes are required for producing an ingot.